Bipolar, batteries employ either one of two types of bipolar electrodes. The first, or face-to-face type of bipolar electrode, utilizes an electrolyte impervious, substantially planar, conductive septum having a first polarity active material on one face thereof and an opposite polarity active material on the opposite face thereof. Bipolar electrodes are typically held in frames of nonconductive material which isolate one cell from the next and which are stacked together (i.e., to form the battery) such that opposite polarity faces of adjacent electrodes oppose each other across in electrolyte-filled gap containing an electrolyte-permeable, dendrite-suppressing separators (e.g., microporous polyethylene, glass mat, microporous PVC, etc.). One such battery is exemplified by the patent to Poe et al U.S. Pat. No. 3,728,158, assigned to the assignee of the present invention.
It is known for the electrolyte-impervious, conductive septum that separates the opposite polarity active materials and one cell from the next to comprise (1) a thin plate of lead or alloy thereof (hereinafter referred to simply as lead), (2) electrically conductive polymer, or (3) a nonconductive polymer having a plurality of rivet-like conductors embedded therein for electrically communicating one face of the septum to the other. The electrically conductive polymers (e.g., metal filled plastics) tend to have poorer electrical conductivity than the lead plates, and the embedded conductor-type septums are costly to produce and susceptible to leakage of electrolyte between cells incident to poor sealing around the rivets. Accordingly, the use of solid lead plates is preferred for long-lived, high power bipolar batteries. One of the disadvantages of the use of lead plate septums, however, is poor adhesion of the active material (e.g., paste), and particularly the positive active material paste, to the lead plate. This problem becomes aggravated with cycling and results in a shortening of the useful life of the battery.
It is an object of the present invention to provide a unique bipolar battery electrode, and related battery, having a lead plate septum wherein at least the face of the septum that engages the positive active material is coated with a fused layer of lead particles for promoting improved adhesion of the positive active material paste to the septum. It is another object of the present invention to provide a process for improving the adhesion of at least the positive active material paste to a lead septum of a lead-acid, bipolar electrode. These and other objects and advantages of the present invention will become more readily apparent from the detailed description thereof which follows.